This invention relates to a fluid ejecting device having a laminated thermal bend actuator.
The applicant has invented a page width printhead which is capable of generating text and images of a resolution as high as 1600 dpi.
The printheads are manufactured in accordance with a technique that is based on integrated circuit fabrication. An example of such a technique is that which is presently used for the fabrication of micro-electromechanical systems.
These fabrication techniques allow the printhead to incorporate up to 84000 nozzle arrangements. The nozzle arrangements are electromechanically operated to achieve the ejection of ink.
In a number of the Applicant""s inventions, the nozzle arrangements incorporate thermally actuated devices which are displaceable within nozzle chambers to eject the ink from the nozzle chambers. Many of the thermal actuators use a combination of materials and a bending action which results from an uneven expansion of the materials. The thermal actuators are manufactured by depositing consecutive layers of material having different coefficients of thermal expansion.
The present invention was conceived to address certain problems associated with such actuators. A significant problem with such actuators is that the different materials can result in bending and bending stresses being set up in the thermal actuator when the thermal actuator is inoperative and exposed to transient conditions. As is known in the field of integrated circuit fabrication, the deposition of material results in a heating of both the material being deposited and the material on which the deposition takes place. The fact that the materials have different thermal expansion characteristics can result in the bending of the laminated structure upon cooling. This is also the case where the materials have different elasticity characteristics. Those skilled in the field of micro electromechanical systems fabrication will appreciate that this is highly undesirable.
According to the invention, there is provided a fluid ejecting device which comprises
a substrate containing drive circuitry,
nozzle chamber walls and a roof wall positioned on the substrate to define a nozzle chamber in which fluid is received and a fluid ejection port from which the fluid is ejected, in use;
a fluid ejecting mechanism that is operatively arranged with respect to the nozzle chamber to act on the fluid in the nozzle chamber to eject fluid from the fluid ejection port;
a thermal bend actuator that is connected to the drive circuitry to receive an electrical signal from the drive circuitry and to provide actuation of the fluid ejecting mechanism,
wherein
the thermal bend actuator has a laminated structure of at least three layers in the form of a pair of opposed, outer layers and at least one inner layer, the outer layers having substantially the same thermal expansion and elasticity characteristics.
The thermal bend actuator may have a single inner layer.
The outer layers of the thermal bend actuator may each be conductive.
At least one of the outer layers of the thermal bend actuator may be connected to the drive circuitry so that said at least one of the outer layers can be heated.
The outer layers may have a higher coefficient of thermal expansion than the inner layer.